Am Sa, 29.12.2007, 13:20, schrieb Bastien ROUCARIES:
>> > I'm still playing around with multivibrators in transient simulation.
>> > This one is nice: attached you will find two identical schematics
>> > produce almost the same netlist. The only difference between the
>> > is the order of the statements. But the results of the transient
>> > simulation are very different. (the first one fails after producing
>> > more-or-less accurate results and the other one runs thru but nothing
>> > vibrates..)
>> > I think the problem is that in the 2nd case the evaluation order of
>> > nodes is different so the transistor is evaluated after the value of
>> > base contact has been calculated, overwriting the initial DC value I
>> > set using the label. Which is quite strange because I thought that my
>> > label
>> > would cause the initial dc analyses to charge the capacitor on this
>> > so
>> > the wire should stay longer on a high voltage that just for step 0.
>> > Whats the error in my understanding of what's going on when doing a
>> > transient simulation of this circuit?
>> This one is also known... And an ugly one, I know.
>> Right now the position in the netlist in fact determines somehow, how
>> nodes are put into the circuit matrix to be solved which in turn may
>> affect the result due to numerical issues.
>> One of the solution of this problem may be to find a way to re-order
>> the matrix to be solved in a way to
>> 1) get a deterministic ordering
>> 2) and find an order which makes the matrix "easier" to solve
>> If someone on the list has a better clue than me right now how to
>> achieve (2) then please tell me. In the qucsator core there is
>> already an sorting algorithm, but this just cares about pairs of
>> +1 and -1 (e.g. voltage sources) and not about the actual node
> Could you please give me the equation to solve?
> I suppose it is an inversion.
Some of the implemented equation system solvers (e.g. LU, QR, SVD)
decompose the matrix, then solve the system using additionally the
> IF so the magic key is preconditionning.
I know :)))
> I can try to help when I will come back form vaccation (ie 2008/01/08).
If you have some precondition-knowledge I would be glad if you can